The Bypass Angioplasty Revascularization Investigation (BARI) is a randomized multicenter clinical trial that compares a strategy of initial percutaneous transluminal coronary angioplasty (PTCA) to that of initial coronary artery bypass graft surgery (CABG) for selected patients with multivessel coronary artery disease. The primary hypothesis tested is that a strategy of initial PTCA is no worse than one of initial CABG with respect to mortality at five years. Other major endpoints include: myocardial infarction, need for repeat procedures and hospitalizations, functional status, radionuclide ejection fraction, quality of life and economic impact. The trial began July, 1987. Investigators from 14 primary sites and 4 satellites have randomized 1,829 patients. Also recruited into a registry were 2,013 patients who were eligible but not randomized and a sample of 422 patients deemed eligible based on their angiogram. Important subgroups represented in the randomized cohort include older adults (43%), women (27%), and African Americans (6%), resulting in the largest number of such patients ever studied in any revascularization trial. Central radiographic laboratory review confirmed three-vessel disease was present in 41% of patients and 73% had three or more significant coronary lesions. Follow-up in the original protocol includes clinic visits, telephone contacts, rest and exercise electrocardiograms, and blood lipids over a period of five years. By July 1993, the first patient will have been followed five years and the last patient followed two years. Both randomized and registry patients, we propose to complete and report 5-year follow-up results, including periprocedural outcome, and extend follow-up to 10 years. To accomplish 10-year follow-up, we will use the same methods of data collection and management and continue the same lines of communication among the clinical sites, central laboratories, the data coordinating center and the NHLBI that have served BARI successfully to this point. The clinical sites will rely on the excellent long-term relationships established with their patients and referring physicians. The request for extension is based on prior observations that the benefit of CABG may be lost between five and 10 years and thus conclusions based on 5 years of follow-up may differ substantially from those observed later. Such differences are of particular importance give the chronic nature of coronary disease and recognition that the age of onset in many subjects may be relatively early. Moreover, the role of PTCA as an adjunct to CABG may only be evident during late follow-up. BARI is the largest and most comprehensive comparison of contemporary PTCA and CABG. Furthermore, its data base will allow extensive analyses to best characterize these popular revascularization procedures. The results of BARI will exert an enormous influence on the practice of medicine for patients with coronary artery disease as we enter the next century.